Climate change will affect Southeast Asian countries, particularly Thailand. There are still insufficient studies on rainfall, streamflow, and future floods in the Upper Nan Watershed, northern Thailand. This study examined how future climate change will affect the rainfall, streamflow, and flooding in the Upper Nan Watershed. SWAT and HEC-RAS models were utilized to assess the future streamflow and flooding in this area. The models used data from 1980–2020, which were taken from seven Upper Nan meteorological stations and two discharge stations. In this study, the impact of future climate change was predicted using three GCMs, under RCP4.5 and RCP8.5 scenarios. The historical data analyzed in this study indicated that rainfall in the study area has a positive trend. Climate change will increase further, from 18% to 19%, which will cause more fluctuations and lead to wetter conditions, both in the wet and dry seasons. Climate change delayed the hydrograph peak and the SWAT-modelled streamflow in the N1 and N64 stations by between 0.3% and 5.1%. RCP8.5 inundated all of the stations more than RCP4.5. Our models showed that in the medium future (2041–2060), the inundated area will be similar to that during the 100-year flood probability. Thus, monitoring and preparation are necessary to avoid repeating the considerable 2011 flood losses in Thailand.

Efektivitas Tutupan Rumput Gajah (Pennisetum purpureum) dalam Mitigasi Erosi Tanah oleh Air Hujan

Need of land that increases with the increase of population and social-economic activities which is not balanced with the availability of land will lead to decrease of agricultural land area and production in an area, and North Kalimantan Province is no exception. The objectives of this study were a) to identify agricultural land conversion, b) to examine agricultural production trend, and c) to analyze effects of land conversion on agricultural production in this particular area. Agricultural land conversion was analyzed using geographic information system. Agricultural production was examined using table of frequencies as presented both in graphic and map forms. The effects of land conversion on agricultural production was analyzed using linear regression. The study results suggest that there was an increase in agricultural land conversion in in North Kalimantan (the rate was 0.04 and the total areas was 32,424 Ha). The analyses by regencies indicate increases in the agricultural land area in Bulungan, Nunukan, and Tana Tidung regencies, while on the contrary a decrease was found in Malinau regency. The agricultural production rate was 0.04. The regression analysis shows a relationship between land conversion and agricultural production in North Kalimantan.

New Yogyakarta International Airport (NYIA) is being constructed in Temon Sub District, Kulonprogo District. It lies on 587.2 ha area in the southern part of Java Island coastal area. Many areas of Kulonprogro coastal area are used for aquaculture of vanname shrimp. In that case, the aquaculture land needs to be cleared for the airport construction necessity and requires compensation. The value of the compensation needs to be right calculated by both sides, regarding the aquaculture land are local community assets. This study uses spatial analysis and visual interpretation. Whereas, the calculation of the acquisition value and income capital value uses Discounted Cash Flow (DCF) method. The result shows the area of aquaculture land which impacted to be cleared is 83 ha, means decreasing of shrimp ponds area in Temon Sub District, Kulonprogo District. The calculation of acquisition value for airport development indicates higher value than the income from the aquaculture activity. The results mean the aquaculture landlords do not incur losses due to the airport development project. These findings can be used for local government and related stakeholders to formulate a policy of aquaculture relocation and to estimate projection for aquaculture land suitability in Yogyakarta coastal area.

The role of agroforestry system is significant for the sustainability of land-use, soil, water, biodiversity, and environmental conservation. The soil microfauna and vegetation pattern are potential as ecosystem indicators to evaluate the quality of the environment. The research was conducted in the catchment area level, using 9 plots with difference stratification of up-stream, mid-stream, and downstream in the catchment. The nested quadrate divides into 6 layers of vegetation, and soil fauna sample is in the middle of the study plot. The soil microarthropods is observed by Berlese fauna method for 7 days and identify order by microscope and counting. The result indicates that the microarthropods in the agroforestry system shown in high abundance and biodiversity. Moreover, the vegetation pattern has a strong correlation with the microarthropods biodiversity. The research found that microarthropods biodiversity and vegetation pattern in the agroforestry system have a strong correlation and interaction. This relation will have a significant role to maintain the ecosystem balance on nutrient and water cycle in the catchment area. Farmers on agroforestry system provide both of environment and economics by following the natural role to support agroforestry system as an ecosystem service.

Merawu watershed is located at Banjarnegara district and categorized as degraded watershed in the Serayu river basin. Upstream area in the Merawu watershed is a mountainous area of 1,500 m a.s.l., with steep slopes and high rainfall intensity. Upstream Merawu has an important function as recharge area, protect the downstream and water supply for the Merica reservoir. Forest conversion to intensive farming practices have produced large portion of erosion, surface runoff and water pollutant. Understanding the surface runoff changes in the forest conversion to intensive farming practices is important. Investigations of direct runoff in the intensive farming system in upstream area of Merawu watershed were observed using two small catchment experiments. Catchment for intensive farming system was compared to non-disturbed catchment of Pine forest. Surface disturbances associated with soil tillage, fertilization, pesticides and mulching during 2-3 months of planting reduced the soil capacity to control rainfall. During 1-year investigation, total direct runoff (DRO) in intensive farming catchment was 360.05 mm or 34.4% of rainfall or 1.63 times higher than that in the Pine forest catchment. Unit hydrograph analysis found the direct runoff coefficient was 9.4% or 1.7 times higher than that in the Pine forest catchment. This study found the important function of canopy interception, forest floor interception, soil management and infiltration to control the direct runoff in the catchment.